Iraqi forces on Thursday (May 26) continued their advance towards Falluja city, a longtime bastion of the Islamic State, intensifying shelling of the city to retake the militant stronghold just west of Baghdad.

Fallujah, a bastion of Sunni Muslim “jihadists” (Islamic State, ISIS , ISIL , IS and Daesh) 50 km (30 miles) from Baghdad, was the first city to fall to Islamic State, in January 2014.

Six months later, the group declared a caliphate spanning large parts of Iraq and neighboring Syria.

"Footage from areas near Sajariya district east of Falluja showed heavy concentrations of Iraqi army, police forces and Shiite militias known as Hashid Shaabi fighters."

Air strikes and mortar salvoes targeted neighborhoods inside the city where Islamic State is believed to maintain its headquarters.

Shiite Muslim politicians stepped up calls on Abadi to attack Falluja after a series of devastating bombings in Baghdad and elsewhere, claimed by Islamic State, an ultra-hardline Sunni Muslim group.

Local Sunni tribes and a coalition of mostly Shiite militias are supporting the army in the battle against Islamic States, whose forces in the city number between 500 and 700, according to a U.S. military estimate.